Ji You Gu

Preparation of Plywood Using Starch Adhesives Modified with Isocyanate

The purpose of the study was to manufacture plywood using starch adhesives modified by isocyanate, the influence factors on the bonding strength and water resistance of starch adhesive were studied by different solid content, adding additives and adding isocyanate. X-ray photoelectron spectroscopy (XPS) analysis was used to characterize the chemical structure of bonding interface. The results show that the bonding strength of starch adhesive was increased significantly when solid content increased to 50%. Bonding strength and water resistance were improved significantly by adding additives and isocyanates to starch adhesive. The analysis of XPS indicated that the chemical bonding derived from the reactions of isocyanate was the key factor to increase bonding strength and water resistance.

Study on Film of Polyvinyl Acetate Emulsion Modified by Starch

The use of starch on polyvinyl acetate emulsion blend modified in order to achieve improved film toughness, which aims to improve water resistance and film-forming emulsion adhesive performance. Dynamic mechanical properties (DMA), scanning electron microscopy (SEM) method was used to analyze the dynamics of film emulsion blend composite mechanics, the distribution of latex particles and glass transition temperature. The results show that: with pure polyvinyl acetate (PVAc) compared to starch-modified film-forming emulsion film distribution, glass transition temperature of the homopolymer emulsion up to 30°C.

Preparation of the Plywood Using UF Resin Modified with Blocked Isocyanates

The plywood was prepared using the UF resin modified with isocyanate blocked by sodium bisulfate in this paper. And the effects of the ratio of UF resin and blocked isocyanate, hybrid method and the additive on the properties of the plywood were also studied. The results showed that under the condition of BPI / UF =5%, the order of urea-formaldehyde resin mixed mode curing agent, additive and finally joined the BPI , the bonding strength of the plywood was improved obviously and the formaldehyde release of the plywood could achieve the demand for the national standard.

The Impact of Different Dosage of Additives on the UF Resin Used in Plywood

Through the study of the effects of different dosage of additives on the properties of urea formaldehyde resin adhesive prepared at low mole ratio of formaldehyde/urea, optimize the synthetic process of the UF resin which is used at the E0 grade plywood. The results showed that the product synthesized under the following condition: the mole ratio of formaldehyde/urea is 0.99:1, the dosage of the specific additive is 1.0% and that of melamine is 3-4%, had a good comprehensive performance and the formaldehyde emission of the plywood meets the E0 grade which is environmental-friendly.

Performances of Polyvinyl Acetate Hybrid Emulsions with Nanoparticles SiO2

Polyvinyl acetate（PVAc）hybrid emulsions with nanoparticles SiO2 were prepared by the semi-continuous seeding emulsion polymerization. The micro-morphologies of the hybrid emulsions, the diameters and distributions of the latex particles were characterized with the aid of scanning electron microscope (SEM) and diameter analyzer. Adhesive properties of hybrid emulsions and the properties of the emulsion films were determined by mechanical properties tester and dynamic mechanics analyzer (DMA). And the rheological behaviors of hybrid emulsions were measured via rheometer. SEM and diameter analysis showed that the process of the nanoparticles SiO2 by ultrasonic made a good dispersibility of latex particles in emulsions, diameters of the latex particles were 0.68~0.89μm with the content of SiO2 from 0 to 1.0% (% in relation to the total mass VAc), and indexes of distributions of particle size were increased with the increasing of the content of SiO2 from 0 to 1.0%. Adhesion strengths of PVAc emulsions modified with nanoparticles SiO2 were improved. DMA results indicated that the films of PVAc/SiO2 hybrid emulsions had the higher storage modulus than the film of PVAc, the temperatures of glass transition of the films of PVAc/SiO2 hybrid emulsions were not changed obviously, and the water absorptions of films were decreased. Rheological results revealed that flow consistency indexes were increased then decreased with the increasing of the content of SiO2 from 0 to 1.0%, and PVAc/SiO2 hybrid emulsions were typical pseudoplastic fluid.

Study on Bonding Performances of Air Plasma Treated FRP

This paper reports on the effect of air plasma on the FRP surface wettability via change of the water contact angle. The aim is to alter the surface in a manner and scale resulting in stronger bonding strength between FRP and wood. The specimens are exposed to the direct current discharge. The irradiation time and power are variables. Goniometry is employed to determine the contact angle of FRP surface. The plasma treatment leads to radical generation and activation of such agents as oxygen, thus the surface contact angle decreases significantly. The shear strength of samples of wood reinforced by treated FRP is also given to show the bond quality at the FRP-wood interface.

Mechanical Properties of Wheat Straw Particleboard Using Composite Adhesives

The purpose of the study was to use a cheap wheat straw to manufacture particleboard. Wheat straws offer great promise and new challenges as replacement for wood in processed wood products. The particleboard was produced using composite adhesive which the urea-formaldehyde (UF) adhesives modified by emulsifiable polymeric methylene diphenyl diisocyanate (EPU). The properties of the particleboard was evaluated by measuring internal bonding strength(IB), thickness swelling, modulus of rupture(MOR), modulus of elasticity (MOE) and formaldehyde emission. The optimal condition was chosen at density of 0.75g/cm3, UF/EPU ratio of 70/30, adhesive amounts of 10% based on the dry amounts of wheat straw. The test results showed that maximum dry internal bonding strength, wetting internal bonding strength, modulus of rupture, modulus of elasticity was 0.45MPa, 0.072MPa, 31.50MPa and 4564MPa, respectively. The thickness swelling (TS2h) and thickness swelling (TS24h) was 3.51% and 11.1%, respectively. The free formaldehyde of wheat straw particleboard reached E0-type national standards.

Relativity Analysis between Dynamic and Static Modulus of Elasticity on Different Thickness Wood-Plastic Structural Plates

The relativity was evaluated between dynamic modulus of elasticity (MOE) and static MOE, in order to assess the potential of using nondestructive testing (NDT) method as a checking tool for mechanical properties of wood-plastic structural plates. The dynamic MOE was evaluated on a FFT system, and the static MOE was determined by three point bending test. All of specimens were made of polyethylene（PE）and poplar flour. A significant correlation between the dynamic MOE and the static MOE was obtained from relativity analysis. These results suggest that the NDT method could be appropriate to estimate the dynamic MOE of specimens with different thickness.

Alkali-Thickening Characteristics of Vinyl Acetate and Vinyl Ester Versatic Acid Copolymer Latex Using Carboxylic Monomers

VAc/Veova10/MAA copolymer latex containing carboxyl groups was synthesized by the semi-continuous seed emulsion polymerization with vinyl acetate (VAc), vinyl ester of versatic acid (Veova10) and methacrylic acid (MAA). Alkali-thickening characteristics of VAc/Veova10/MAA copolymer latex containing carboxyl groups, adjusted from pH 5.5 to 6.4, 8.9, 9.8 with NaOH aq., were investigated by DSC. The results showed that the viscosities of VAc/Veova10/MAA copolymer latex were increased with the inceasing of pH, The frozen temperature peaks were observed to increase with the increasing of pH, the thawed temperature peaks were shifted to lower temperature, and the state of water in latexes were different. The partial morphologies of latexes were irregular and latexes were pseudoplastic fluid. And water absorption of films were increased with the increasing of pH in latexes and dry and wet shear strengths were also decreased.

Preparation of Particleboard Made from Wheat Straw with Low-Formaldehyde-Emission Composite Adhesive

This research attempted to prepare the E0 type wheat straw particleboards with low emission formaldehyde composite adhesive. The composite adhesive combined UF resin and blocked polyisocyanate with low deblocked temperature was synthesized with sodium bisulphate as blocking agent. The effects of different blocking agents, mol ratio, reaction temperature and time on block reaction were studied. The influence of mixed ratio of composite adhesive on the performance of wheat straw particleboard was investigated.